Biomedical subjects

R Ramos

Publications and source records attributed to R Ramos.

At least 19 recordsLinked to original sources

PubMed1992

In vitro evaluation of a novel chemotherapeutic agent, Adozelesin, in gynecologic-cancer cell lines.

Adozelesin is a derivative of an extremely cytotoxic compound, CC1065. This entirely new class of drug binds preferentially to DNA and facilitates alkylation reaction. In the present study, we used the adenosine triphosphate (ATP) chemosensitivity assay to compare the cytotoxic potency of Adozelesin with that of common chemotherapeutic agents in ten gynecologic-cancer cell lines. Flow cytometry was also used to study its effects on cell-cycle kinetics. The mean drug concentrations required to produce a 50% reduction in ATP levels as compared with controls [IC50] were: Adriamycin, 0.17 +/- 0.06 microM; 4OH-Cytoxan, 18 +/- 3 microM; cisplatin, 17 +/- 7 microM; 5-fluorouracil, 183 +/- 116 microM; and Adozelesin, 11.0 +/- 5.4 pM. Thus, Adozelesin was 10(4) - 10(7) times more potent than Adriamycin, cisplatin, 5-fluorouracil, and Cytoxan. Cell kinetics studies revealed significant S and G2 blocks such as those previously reported for other alkylating agents.

Adenocarcinoma↗

PubMed1992

Spectrum of cell-cycle kinetics of alkylating agent adolezesin in gynecological cancer cell lines: correlation with drug-induced cytotoxicity.

Adolezesin is an analog of CC-1065. These compounds are among the most potent alkylating agents known to date. Currently Adolezesin is undergoing phase I clinical trials at several cancer centers in the USA. While the cytotoxic effects of Adolezesin have been addressed elsewhere, its effects on cell-cycle kinetics have not been reported. Flow cytometry was performed on five human gynecological cancer cell lines: AN3, AE7, BG1, HEC1A, and SKUT1B. Exposure to Adolezesin (U73975, Upjohn Co.) was done at near confluency at 0, 0.1, 0.2, 0.5, 1 and 5x, with x = 10 pg/ml as reference concentration, for 90 min. Cell samples were taken by trypsinization at 0, 24, 48, 72, 96, and 168 h for flow cytometry. The ATP chemosensitivity assays were performed on the above cell lines to establish dose/response curves. Flow-cytometric analyses revealed that there was a spectrum of cell-cycle perturbations, which included biphasic S and G2 blocks, reverse dose-dependent G2 blocks, and a sequential relationship of S and G2 blocks. This study demonstrated that the cell kinetic response to Adolezesin depended on several variables such as cell lines, drug sensitivity, concentrations, and sampling time. Because of this multivariable dependence and the lack of correlation with cytotoxicity, it would be difficult to use cell kinetic pertubations to predict chemotherapeutic response.

Adenosine Triphosphate↗

PubMed1992

Comparison of U-73,975 and cisplatin cytotoxicity in fresh cervical and ovarian carcinoma specimens with the ATP-chemosensitivity assay.

U-73,975 (U-73), a closely related synthetic analogue of the antitumor agent CC-1065, acts by binding tightly in the minor groove of DNA. A comparison was made between the cytotoxicity of U-73 and cisplatin (DDP) on 11 fresh cervical and 7 fresh ovarian carcinoma specimens. The ATP-chemosensitivity assay as previously described (Sevin et al. Gynecol. Oncol. 31, 191-204, 1988) was used to determine the cytotoxic effect of U-73 and DDP. IC 50s were calculated using regression analysis. The mean IC 50s for U-73 and DDP were 519 pg/ml and 2918 ng/ml, respectively, for the cervical carcinoma specimens and 324 pg/ml and 2649 ng/ml, respectively, for the ovarian carcinoma specimens. Significance comparing U-73 and DDP for cervical and ovarian tissue was demonstrated with P < 0.001. U-73 was 4000 times as cytotoxic per unit of mass as DDP on cervical carcinoma compared to over 8000 times for ovarian carcinoma. Based on these in vitro data, U-73 appears to be a very promising antitumor agent for cervical and ovarian carcinoma.

Adenosine Triphosphate↗

PubMed1992

Determination of hormonal response in uterine cancer cell lines by the ATP bioluminescence assay and flow cytometry.

Although progesterone receptor status has been shown to correlate with response to hormonal therapy, not all progesterone receptor-positive patients respond to this treatment and additional biologic assays are needed to help better predict clinical response to hormonal therapy. This study explored the potential of the ATP bioluminescence assay and flow cytometry as biological assays of hormonal response. Five uterine cancer cell lines were used: AE7, ECC-1, HEC1A, AN3, and SKUT1B. Cells were exposed to Provera or tamoxifen at 0.1, 0.2, 0.5, 1, 2, and 5X (X equal to peak plasma concentrations: 1.0 micrograms/ml Provera and 0.1 micrograms/ml tamoxifen). For correlation, estrogen and progesterone receptors were determined by the standard dextran-coated charcoal method. Only AE7 and ECC-1 were positive for progesterone receptors (501 fmol/mg AE7, 194 fmol/mg ECC-1) and the rest were negative (less than 8 fmol/mg). Tamoxifen exerted no inhibition to the above cell lines. Meanwhile, Provera exerted dose-response inhibition on both AE7 and ECC-1 cell lines. The effects of accumulation of G0-G1 phase and reduction of S, G2 cells (P less than 0.05), but not on the HEC1A cell line (P = 0.4). These changes confirmed the antiproliferative property of Provera. Further studies are needed to establish the role of the ATP bioluminescence assay and flow cytometry as biological assays of hormonal response.

Adenocarcinoma↗

PubMed1992

The use of ATP bioluminescence assay and flow cytometry in predicting radiosensitivity of uterine cancer cell lines: correlation of radiotoxicity and cell cycle kinetics.

Radiotherapy remains an important part of uterine cancer treatment. This study was designed to evaluate the potential of the ATP bioluminescence assay and flow cytometry for predicting radiosensitivity. Correlation of these two modalities revealed important insights into the relationship of radiotoxicity and cell kinetic effects. Six human uterine cancer cell lines were used: AE7, ECC1, HEC1A, HEC1B, AN3, and SKUT1B. Doses of cobalt 60 were 0, 1, 2, 5, 8, and 10 Gy. The ATP bioluminescence assays were performed on Day 7. Cell samples were taken at 0, 24, 48, 72, 96, and 168 hr for flow cytometry. The linear-quadratic model was used to fit survival data and mean inactivation dose D was calculated. Among parameters such as D, alpha and beta coefficients, and surviving fraction at 2 Gy (SF2), both D and SF2 correlated best with survival data. Radiation effects on the cell cycle did not correlate with D and revealed two distinct patterns: either a G1 accumulation with mild G2 block or a G1 depletion and severe G2 block. The S cells consistently demonstrated a biphasic pattern with an initial reduction followed by an accumulation. In summary, the ATP assay was shown to have potential in the study of radiosensitivity. Radiation-induced cell kinetics appeared to vary with intrinsic cellular differences and, thus, could not be used to predict radiosensitivity.

Adenosine Triphosphate↗

PubMed1992

Comparative evaluation of pirarubicin and adriamycin in gynecologic cancer cell lines.

Pirarubicin (PIRA) has been shown to have improved potency with less cardiac toxicity in several phase I and II clinical trials in Japan and Europe. Since Adriamycin (DXR) remains one of the most potent drugs in treatment of gynecologic cancers, this derivative has the potential to become an important chemotherapeutic agent. In this study, we compared the performance of these two drugs against a panel of 10 gynecologic cancer cell lines. The ATP chemosensitivity assays were used to determine dose-response curves. Flow cytometry was used to study cell kinetic response to both drugs. Using an IC50 value of 0.2 micrograms/ml as a cutoff for drug sensitivity, 4 cell lines, ECC1, HEC1B, BG1, and SKOV3, were considered resistant to DXR. By comparing IC50s, PIRA was 3.4 +/- 0.4 times more potent than DXR (P = 0.05). The other 6 cell lines, AN3, AE7, HEC1A, CAOV3, SKUT1B, and ME180, were considered sensitive to DXR. In this group of cell lines, PIRA was 1.6 +/- 0.3 times more potent than DXR (P = 0.5). Both PIRA and DXR elicited a spectrum of cell kinetics. By comparing the magnitude of G2 blocks at 0.1 micrograms/ml, PIRA was approximately 2-5 times more potent than DXR in SKUT1B, HEC1A, and BG1 cell lines. PIRA also displayed a reverse dose-response pattern of G2 block so that at high dose, cell cycle kinetics would mirror those of untreated controls. This observation supports the presence of a resistant tumor subpopulation and the concept of tumor heterogeneity.

Antibiotics, Antineoplastic↗

PubMed1992

Virulent diverticular disease in young obese men.

Recent treatment of young patients (aged 40 years or less) with complicated diverticulitis prompted us to review our experience. During a 9-year period ending in December 1990, 61 of 238 patients treated for acute diverticulitis were 40 years of age or younger. The younger patients were primarily obese Hispanic males in whom the correct diagnosis was frequently missed. Younger patients more frequently required an operation on an urgent basis for complications of diverticulitis during the initial hospitalization. The most common indication for operation in young patients was perforation compared with recurrent disease for the older age group. The younger group had a sevenfold incidence of enteric fistulas complicating their acute episode of diverticulitis. Our data suggest that diverticular disease in young patients is more common and more likely to require early surgical intervention than previously noted. In addition, obesity may represent an important etiologic factor in the development of diverticular disease.

Adult↗

PubMed1992

Laparoscopic colectomy.

Fifty-one laparoscopic colectomies were attempted at two institutions. The clinical results and methods are presented. Seven cases (14%) were converted to facilitated procedures, and four cases (8%) were converted to "open." Cases of cancer, diverticulitis, endometriosis, regional enteritis, villous adenomas, and sessile polyps were operated. Right, transverse, left, low anterior, and abdominoperineal colectomies were performed. Colotomies and wedge resections were also performed. Laparoscopic suturing was required in five cases of incomplete anastomosis by circular stapler (18%). Suturing was required in all right, transverse colectomies and colotomies. Operative time averaged 2.3 hours. Hospitalization averaged 4.6 days. Four patients had complications (8%), and one 95-year-old died of pneumonia (2%). Laparoscopic colectomies can be performed safely, but require two-handed laparoscopic coordination, as well as suturing and knot-tying skills.

Adult↗

PubMed1991

Octadecyl silica: a solid phase for protein purification by immunoadsorption.

Immunoaffinity chromatography involves binding of an antigen or antibody to a solid matrix, usually agarose, frequently using the cyanogen bromide method. These methods are laborious, rather expensive, and their use has been mostly restricted to immunopurifications on the microscale. We propose here the use of octadecyl silica (SiCl8) beads, a matrix for HPLC, as an alternative solid phase for protein immunopurification and immunoadsorption. Antibodies or antigens are strongly bound to SiCl8 by a simple incubation; radiolabeled antibodies can only be eluted from SiCl8 by detergent-containing solutions. After the remaining free binding sites have been saturated with bovine serum albumin, SiCl8 is incubated with the antigen- or antibody-containing crude preparations and is then poured into a minicolumn. The nonspecifically bound proteins are removed by washing; specific proteins are eluted by disruption of the antigen-antibody complexes with a low pH buffer. With this methodology, we have obtained high purity preparations of proteins in single steps, even when these proteins are present in trace amounts (picograms) in a complex mixture such as human serum. Similarly, specific antibodies against an intracellular parasite (Trypanosoma cruzi) were completely absorbed from human serum with SiCl8 coated with parasite antigens.

Animals↗

PubMed1991

Characterization of in vitro chemosensitivity of perioperative human ovarian malignancies by adenosine triphosphate chemosensitivity assay.

We report the in vitro chemosensitivity of primary and recurrent human ovarian tumor samples analyzed by adenosine triphosphate chemosensitivity assay. We defined sensitivity as a greater than or equal to 70% decrease in intracellular adenosine triphosphate versus control at 20% of the reported peak plasma concentration per agent tested. Twenty of 21 assays (95.24%) were completed successfully. Single-agent and combined dose-response patterns consisting of decreasing viability with increasing drug concentration were observed consistently. Thirteen primary tumors were assayed, with 15.4% sensitive to cisplatin, 7.7% sensitive to 4-hydroxycyclophosphamide and 53.8% sensitive to their combination. Seven recurrent tumors were assayed, with 14.3% sensitive to cisplatin, 28.6% sensitive to 5-fluorouracil, and 42.9% sensitive to their combination. Dose-response characteristics and in vitro sensitivity rates reported in this article are consistent with reports of patient response in the literature. We conclude that adenosine triphosphate chemosensitivity assay is an efficient and reliable instrument for the in vitro chemosensitivity assessment of human tumors and warrants further clinical investigation.

Adenosine Triphosphate↗

PubMed1991

Timing of postpartum tubal sterilization using the Filshie clips: an analysis of data from two developing-country centers.

Two-hundred-ninety-seven women at a Panamanian center and 148 women at a Philippine center had their tubal sterilization performed during their postpartum hospital stay after an uncomplicated vaginal delivery of a live birth. The sterilizations were all performed with the use of the Filshie clip via minilaparotomy. The timing of the sterilization varied from two hours to six days after delivery. At each of the two centers, women sterilized within 48 hours after delivery were compared with those sterilized at 49 or more hours with respect to surgical difficulties, tubal injuries, complications/complaints, technical failures and lengths of hospitalization after sterilization and before discharge. The one-year gross cumulative pregnancy rates were also compared. No significant differences were detected in any of the above outcome variables between the two timing groups at each center. While the data suggest that tubal sterilizations by the Filshie clip performed two to six days following childbirth are as safe and effective as those performed within 48 hours of delivery, further studies are urged.

Developing Countries↗

PubMed1991

Cell kinetic perturbations after irradiation and caffeine in the BG-1 ovarian carcinoma cell line.

The treatment of ovarian carcinoma includes maximum surgical removal of the tumor tissue followed by irradiation or chemotherapy. In this study, the effects of caffeine on cell cycle traverse have been studied over a 168-hr period after X irradiation in BG-1 cells, an ovarian carcinoma cell line. The results were obtained with dual-parameter flow cytometric measurements of DNA and nuclear protein, using propidium iodide and fluorescein isothiocyanate. After radiation alone, a dose-related arrest of cells in G2 phase and cell kill were observed. Irradiating BG-1 cells with 5 Gy produced an accumulation of the cells in G2 at 24-72 hr postirradiation. When G2 was divided into low nuclear protein (G2A) and high nuclear protein (G2B) compartments, there was a G2A peak accumulation at 24 hr and a G2B peak accumulation at 48-72 hr. The addition of 1 mM caffeine to the culture media, starting immediately postirradiation, prevented G2 arrest, promoting a rapid traverse of cells through G2A to G2B to G1, which was associated with diminished survival.

Caffeine↗

PubMed1991

In vitro enhancement of cis-platinum antitumor activity by caffeine and pentoxifylline in a human ovarian cell line.

Cell kinetic perturbations measuring DNA and nuclear protein with dual-parameter flow cytometry were studied in vitro after cis-platinum (DDP) treatment of a DDP-resistant human ovarian cell line (BG-1). Cell viability (trypan blue exclusion) and the cell's ability to replicate (replicating potential) are also reported. A dose-dependent G2 arrest and concomitant increase in cytotoxicity were observed. We also observed a marked increase in cytotoxicity of 2.5 micrograms/ml DDP with the addition of 1 mM of caffeine (CAF) or pentoxifylline (PTX). Additionally, the cells treated with DDP and CAF or DDP and PTX demonstrated a markedly diminished ability to replicate. Cell cycle perturbations, especially the G2-phase arrest, were markedly enhanced in the cells treated with DDP and CAF or DDP and PTX, when compared to that in cells treated with DDP alone. We conclude that the cytotoxicity of DDP is enhanced by CAF and PTX in vitro by inhibiting DNA repair during the S and G2 phases.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1991

The effects of Provera on chemotherapy of uterine cancer cell lines.

Even though progestin is commonly added to many chemotherapy regimens in the treatment of uterine cancers, its role is still unproven. Since progestin is antiproliferative, its tendency to arrest cells in G1 phase may interfere with cytotoxic mechanisms. The ATP chemosensitivity assay and flow cytometry were used to study the effects of a progestational compound such as Provera on three single agents and four drug combinations. Uterine cancer cell lines included progesterone-receptor (PR)-positive AE7 and ECC1 and PR-negative HEC1A, HEC1B, AN3, and SKUT1B. Provera selectively affected only PR-positive cell lines. It imposed an antiproliferative effect on drug-induced cell-cycle perturbations by reducing G2 and S blocks and minimizing G1 depletion. When using IC50s (concentrations required for 50% growth inhibition) of 0.5 as a cutoff for drug sensitivity and resistance, Provera significantly improved the IC50s of the drug-resistant subgroup from 1.95 +/- 0.36 to 0.71 +/- 0.19 (P = 0.009) but not those of the drug-sensitive subgroup (P = 0.13). In summary, Provera appeared to work independently from cytotoxic mechanisms. Its improvement of cytotoxicity was most pronounced in resistant cell lines bearing progesterone receptors.

Antineoplastic Agents↗

PubMed1991

Active site-blocked factor IXa prevents intravascular thrombus formation in the coronary vasculature without inhibiting extravascular coagulation in a canine thrombosis model.

To assess the contribution of Factor IX/IXa, to intravascular thrombosis, a canine coronary thrombosis model was studied. Thrombus formation was initiated by applying current to a needle in the circumflex coronary artery. When 50% occlusion of the vessel developed, the current was stopped and animals received an intravenous bolus of either saline, bovine glutamyl-glycyl-arginyl-Factor IXa (IXai), a competitive inhibitor of Factor IXa assembly into the intrinsic Factor X activation complex, bovine Factor IX, or heparin. Animals receiving saline or Factor IX developed coronary occlusion due to a fibrin/platelet thrombus in 70 +/- 11 min. In contrast, infusion of IXai prevented thrombus formation completely (greater than 180 min) at doses of 460 and 300 micrograms/kg, and partially blocked thrombus formation at 150 micrograms/kg. IXai attenuated the accumulation of 125I-fibrinogen/fibrin at the site of the thrombus by approximately 67% (P less than 0.001) and resulted in approximately 26% decrease in serotonin release from platelets in coronary sinus (P less than 0.05). Hemostatic variables in animals receiving IXai, remained within normal limits. Animals given heparin in a concentration sufficient to prevent occlusive thrombosis had markedly increased bleeding, whereas heparin levels that maintained extravascular hemostasis did not prevent intracoronary thrombosis. This suggests that Factor IX/IXa can contribute to thrombus formation, and that inhibition of IXa participation in the clotting mechanism blocks intravascular thrombosis without impairing extravascular hemostasis.

Animals↗

PubMed1991

An immunogenetically defined and immunodominant Trypanosoma cruzi antigen.

Two strains of mice, A. SW (H-2s) and A.CA (H-2f), were immunized with live trypomastigotes or epimastigotes of the Tulahuen strain of Trypanosoma cruzi or with their sonicates. By immunowestern blotting, sera from A.SW mice, but not from A.CA, recognized, in an immunodominant fashion, a 45 kDal polypeptide (Tc45) present in both epimastigotes and trypomastigotes. Since A.SW and A.CA strains are congenic for the major histocompatibility H-2 complex, recognition of Tc45 seems to be controlled by this genetic region or by gene(s) located in its immediate vicinity. Subcellular fractionation revealed that Tc45 is mainly present at the cytoplasmic compartment.

Animals↗

PubMed1991

Helicobacter pylori in Barrett's esophagus.

Barrett's esophagus is an anatomicoclinical state in which, due to the prolonged action of gastroesophageal reflux, the squamous epithelium is replaced by columnar epithelium. Helicobacter pylori has been implicated in the pathogenesis of various gastrointestinal disorders and has occasionally been observed in Barrett's esophagus. The aim of this study is to determine the incidence of H. pylori in Barrett's esophagus and try to establish its role in the pathogenesis of this disorder. H. pylori was observed in 31 biopsies (44.3%) of the 70 studied, mainly when the epithelium is of the gastric atrophic-fundic type (p less than 0.01). Its presence shows no relation to the degree of inflammatory activity and does not seem, therefore, to play an important role in the pathogenesis of the lesion.

Adult↗

PubMed1991

Comparative efficacy of short-term versus long-term cefoxitin prophylaxis against postoperative infection after radical hysterectomy: a prospective study.

We report the results of a randomized, double-blind comparison of short-term versus long-term cefoxitin prophylaxis against infections after radical abdominal hysterectomy with pelvic and para-aortic lymphadenectomy. Of 113 evaluable patients, 54 (47.8%) received short-term (three doses) and 59 (52.2%) long-term (12 doses) prophylaxis with intravenous cefoxitin (2 g per dose). No significant differences in demographics, preoperative risk factors, or clinical course were detected between the two groups; nor did we detect significant differences in the incidence of surgical-site-related infections (7.4 versus 5.1%, respectively, P = .61), postoperative urinary tract infection, or other febrile morbidity. We conclude that short-term and long-term cefoxitin prophylaxis are equally effective for the prevention of post-operative surgical-site-related infections after radical hysterectomy.

Adult↗